Highly branched and loop-rich gels via formation of metal-organic cages linked by polymers.
Highly branched and loop-rich gels via formation of metal-organic cages linked by polymers.
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DOI：
10.1038/nchem.2390
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发表时间：
2016-01
期刊：
影响因子：
21.8
通讯作者：
Johnson JA
中科院分区：
文献类型：
--
作者：
Zhukhovitskiy AV;Zhong M;Keeler EG;Michaelis VK;Sun JE;Hore MJ;Pochan DJ;Griffin RG;Willard AP;Johnson JA
通过金属-配体配位形成的凝胶通常具有非常低的支化官能度 f，因为它们由〜2-3个聚合物链组成，这些聚合物链与作为连接点的单个金属离子相连。因此，这些材料非常柔软，无法承受诸如悬空端和环等网络缺陷。我们在这里报告了一种由聚合物配体和金属有机笼（MOC）作为连接点组装而成的新型凝胶。由此产生的“polyMOC”凝胶可精确调节，并可能具有增强的分支功能。我们展示了这种聚 MOC 的两个例子：一种基于 M2L4 桨轮簇连接的低 f 凝胶和一种基于 M12L24 笼的高 f 组成异构体凝胶。后者具有大的剪切模量，但也有大量的弹性非活性环缺陷，我们随后将其交换为功能配体，而对凝胶的剪切模量没有影响。这种配体取代在低f凝胶中是不可能的，包括基于M2L4的polyMOC。
Gels formed via metal–ligand coordination typically have very low branch functionality, f, as they consist of ∼2–3 polymer chains linked to single metal ions that serve as junctions. Thus, these materials are very soft and unable to withstand network defects such as dangling ends and loops. We report here a new class of gels assembled from polymeric ligands and metal-organic cages (MOCs) as junctions. The resulting ‘polyMOC’ gels are precisely tunable and may feature increased branch functionality. We show two examples of such polyMOCs: a gel with a low f based on a M2L4 paddlewheel cluster junction and a compositionally isomeric one of higher f based on a M12L24 cage. The latter features large shear moduli, but also a very large number of elastically inactive loop defects that we subsequently exchanged for functional ligands, with no impact on the gel's shear modulus. Such a ligand substitution is not possible in gels of low f, including the M2L4-based polyMOC.